Electrode structure for electric discharge devices



' Feb. 20, 1951 Y K. c. DE WALT 2,542,639

ELECTRODE STRUCTURE FOR ELECTRIC DISCHARGE DEVICES Filed Nov. 23, 1948 Inventor: Kenneth C. DeWalt,

His Attorneg.

Patented Feb. 20, 19 51 UNITED STATES PATENT OFFICE ELECTRODE STRUCTURE FOR ELECTRIC DISCHARGE DEVICES Kenneth C. De-Walt, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application November 23, 1948, Serial No. 61,673

'2 Claims. (Cl. 250--27.5)

dissipate the heat generated in "a compact structure having suitable capacitive and inductive characteristics for the frequencies required. It has also been difficult tojobtain high operating efficiencies in these high power tubes'and this has still further increased the difficulty in producing the compact structure required for the high power, high frequency applications. In accordance with an important'aspect of my'invention, I provide an improved grid structure whichgreat- 1y improves the electrical characteristics of the device, such as the efiiciency at maximum power output, as well as the ability of the signal or control grid to maintain the anode current at reduced anode voltage. The tube ofiers superior characteristics particularly in grounded grid circuits in the way of improved screening wh ch is accomplished in these circuitsby the control 'or signal grid structure while, at the same time, maintaining the current collected by the grid at a minimum.

It is an object of my invention to provide a high efiiciency triode type of electric discharge device particularly adapted for use in grounded grid circuits.

It is another object of my invent on to provide an improved electric discharge device having a high operating efiiciency.

It is a still further object of my invention to provide an improved electric discharge device in which the grid-anode voltage characteristic for concentric output is substantially fiat over a wide operating range.

Further objects and advantages of my invention will become apparent as the following description prcceeds, reference being had to the accompanying drawing, and its scope will be pointed out in the appended claims. In the drawing Fig. 1 is an elevational view insection of a preferred embod ment of my inventiom-and Fig. 2 is a sectional view taken along the line 2-2 and showing the cathode and grid structures.

Referring now to the drawing, I have shown my invention-embodied in the high power transmitting type of electric discharge. device in which a generally cylindrical anode I closed at on end forms a part of the envelope. The anode is preferably formed of copper or similar material and is provided intermediate the ends with an outwardly extending collar2 which may,to advantage, be formed of a good glass sealing material,

of the cathode supporting conductor such as one of the iron-nickel-cobalt alloys. As illustrated, the portion 3 of the anode extending beyond the collar 2 provides a shield which protects the seal formed between the collar 2 and the body portion of the envelope provided by a glass cylinder 4. The envelope is completed by alternate conducting and insulating sections provided by metal members 5, 6 and l and insulating cylnders Band 9, preferably formed of glass. The metal members 5, 6, and l are preferably formed of the same material as the collar '2 and provide externally accessible connections for the grid and cathode and the discharge device. As illustrated, the member 5 is generally of Z-shape cross-section in a radial plane with the free ends of the Z sealed respectively to the upper edge of the cylinder 4 and the lower edge of cylinder 8. The terminal member 6 is,in a similar way, sea ed at its free edges to the upper edge of the cylinder 8 and the lower edge of the cylinder 9. The terminal l is a shallow cup-shaped member with its free edge sealed to the upper edge of the member I.

In high frequency circuit applications some difliculty is encountered by excessiv heating of the glass part 4 of the envelope. To avoid this difficulty, the central portion of the member 4 is preferably made of a low dielectric loss glass and the end portions 4a and 4b of a glass which seals well to the metal members 2 and 5.

The cathode of the device is supported from the terminal members 6 and 1, respectively, by a pair of conductors l0 and H arranged in concentric relation and bonded respectively to the inner surface of the terminal members 6 and I. The cylinder it is hollow and of substantially larger diameter than member II. It is provided at the lower end with a disk-like support [2 to which a number of conductors H are joined. These conductors are arranged in a circular array andjin alternate relaton with respect to a cylindrical array of openings i4 through which alter- I5 extend. The conductors l5 are joined to a disk-like member [6 which is bonded tovthe lower end of the other cathode supporting member ll. As illustrated in the drawing, th cathode supportin conductors l3 and I5 are joined at their lower ends of the cathode conductors proper, designated by the numeral ll, which are arranged in a cylindrical array. As best shown in Fig. 2, the cathode conductors are-provided by. the arms of a plurality of U-shaped conductors which are threaded through suitable openings in a supporting disk I 8. The cathode structure just described is maintained under suitable tension by a tensioning arrangement including a central rod or post 19 which is fixed at one end in the lower end H and which extends through an opening in the lower cathode disk l8. The post 19 is of substantially vided in the cathode supporting conductor ll.

The spring bears at its lower end on a suitable flange 24 bonded to the upper end of the sleeve 2|. It will be apparent that the members 6 and I provide terminals for the cathode, each of which is connected with alternate ones of the cathode conductors so that these conductors may be energized with each half of the conductors arranged in a parallel group which is energized in series with the other group.

In accordance with the important aspect of the present invention, I provide a control or sgnal grid structure which subjects the electron stream to a control field throughout a substantial radial distance. As illustrated in the drawing, this structure comprises two substantially identical grid structures each including a plurality of grid conductors 25 and 26, respectively, arranged in cylindrical arrays and joined at their lower ends to grip caps 21 and 28. At their upper ends, the grids are bonded to concentrically ar ranged collars 29 and 30 having outwardly extending flanges at their upper ends. The two collars are supported from the grid terminal of the envelope by means of a single conical conducting support 3| bonded at its upper end to wires and to enhance the beam forming action of the grid conductors, the grid wires 25 and 26 as well as the helical windings 34 are arranged in alignment.

In a particular embodiment of my invention, the grids were made with the following dimensions:

Outer Inner Grid Grid Mean diameter, Inches 2. 700 2. 328 No. of side rods 8 8 Size of side rods, "Inches" .040 040 Size of winding do. .007 007 Turns per inch 5. 5 5. 5

These dimensions were employed with a cathode having a mean diameter of the cylindrical array of conductors of 2 inches and an anode havin an internal diameter of 4 inches. It will be noted that the corresponding spacing and sizes of the conductors of the two grids are the same so that the grid conductors may be aligned and in this way the collection of electrons by these conductors is minimized as is apparent from an inspection of Fig. 2. The grid conductors are also arranged so that the cathode conductors lie between the adjacent longitudinally extending grid conductors.

An externally accessible terminal for the oath-- ode terminal 6 is provided by a cylindrical conducting member 35 which is bonded to the intermediate portion of the terminal 6 and a terminal member 36 is bonded to the end of the cup-shaped member 1. A longitudinal bore extending through the member I and into the internally positioned cathode supporting conductor l l communicates with the interior of the envelope through lateral passages 31 and provide means for evacuating the device. The passage is closed by a metal tubulation 38 which is welded or otherwise sealed off at its outer end. The tubulation is protected by a suitable cap or thimble 39 which is threaded into the member I.

As an indication of the improvement in operation effected by the novel grid construction of the present invention, a tube employing only the inner. grid required a driving power of 90 kilowatts to produce a peak power output of 582 kilowatts, and with the aligned dual grid construction, as illustrated, the same tube produced an output of 852 kilowatts with the same driving power of 90 kilowatts. The eiliciency of the tube also greatly improved being in the order of 75-80% as compared to for the triode design.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and

I, therefore, aim in the appended claims to cover all such changes and modifications as :fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric discharge device of the triode type including an electrode assembly consisting essentially of a cathode, an electrostatic signal control grid assembly and an anode supported in mutually spaced and insulated relation in the order named with respect to the electron path of the device, said signal control grid assembly including two sets of conductors supported in spaced and aligned relation in the direction of the electron path between the cathode and anode to reduce the signal control grid driving power required with respect to the power required with a control grid consisting of a single set of conductors.

2. An electric discharge device of the triode type including an electrode assembly consisting essentially of a circular array of elongated oathode conductors, a cylindrical signal control grid struuture and a cylindrical anode supported in radially spaced and insulated relation, said signal control grid structure including two sets of elongated conductors supported in radially spaced relation and in circumferential alignment, the two sets of conductors of said signal control grid structure being circumferentially displaced with respect to the cathode conductors, and a common conducting support for the conductors of said control grid structure.

KENNETH C. DE 'WALT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,006,716 Parker July 2, 1935 2,217,417 Peterson Oct. 8, 1940 2,455,846 West Dec. '7, 1948 

